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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education

CO-ORDINATED SCIENCES 0654/62

Paper 6 Alternative to Practical October/November 2011

1 hour

Candidates answer on the Question paper

No Additional Materials are required.

READ THESE INSTRUCTIONS FIRST

Write your Centre number, candidate number and name on all the work you hand in.

Write in dark blue or black pen.

You may use a soft pencil for any diagrams, graphs, tables or rough working.

Do not use staples, paper clips, highlighters, glue or correction fluid.

DO NOT WRITE IN ANY BARCODES.

Answer all questions.

At the end of the examination, fasten all your work securely together.

The number of marks is given in brackets [ ] at the end of each question or part question.

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1 A student performed an experiment to investigate what affects the diffusion of acid into agar. Agar blocks of three different sizes (Fig. 1.1) were cut. The agar contained phenolphthalein indicator and alkali and so was pink in colour.

20 mm

10 mm

10 mm

10 mm

10 mm

10 mm

10 mm10 mm

10 mm

cut on dotted line

cut on dotted line

cut on dotted line

test-tube A

5 mm10 mm

10 mm

5 mm5 mm

10 mm

5 mm5 mm

10 mm

5 mm10 mm

10 mm

test-tube B

test-tube C

discard Fig 1.1 He placed each agar block into 20 cm3 hydrochloric acid in separate test-tubes labelled A,

B and C. The time taken for each block to become colourless (see Fig. 1.2) was then recorded. This is the point at which the acid reaches the centre of the block (Fig. 1.3).

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hydrochloricacid

colourless agar block

Fig. 1.2

test-tube A test-tube B test-tube C Fig. 1.3 (a) (i) Use the stopclocks shown in Fig. 1.3 to record, in Table 1.1, the times taken, in

seconds, for the blocks to become colourless. [2] Table 1.1

tube A B C

cube dimensions / mm 10 x 10 x 10 10 x 10 x 5 10 x 5 x 5

volume of block / mm3 1000 500 250

surface area of block / mm2 600 400 250

surface area / volume ratio

time taken for block to go colourless / s

(ii) Explain why the blocks go colourless.

[2]

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(iii) Calculate the surface area : volume ratio for each block using the formula given and record them in Table 1.1.

volume of block / mm3

surface area of block / mm2

ratio =

[1] (iv) Explain the effect that decreasing the volume of the blocks has on the time taken

for the blocks to become colourless.

[2]

(b) Fig. 1.4 shows a cross section through the human ileum and a magnified image of one

villus.

Using your answer to (a)(iv) and your own knowledge, explain how rapid diffusion of substances into the blood is ensured by the structure of the ileum and villi.

epithelium

bloodcapillary

lacteal

villusileum

Fig. 1.4

[3]

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2 A student carries out the following tests on solid X, which contains two metal salts. Complete Table 2.1, which shows the tests on solid X and the student’s observations and

conclusions.

Table 2.1

test observation conclusion

(a) Mix one spatula full of solid X with solid calcium hydroxide in a test-tube. Heat gently.

(i) Test the gas with moist red litmus paper.

[1]

ammonia gas is given off

(ii) Hold a glass rod dipped in concentrated hydrochloric acid in the gas.

white smoke

is formed.

[1]

(b) Prepare a dilute solution of X in distilled water.

(i) To a portion of the solution of X, add dilute sodium hydroxide until there is no further reaction.

[2]

solid X contains zinc ions

(ii) Acidify a fresh portion of the solution of X with dilute nitric acid, then add barium chloride solution.

white precipitate

[1]

(iii) Acidify a fresh portion of the solution of X with dilute nitric acid, then add silver nitrate solution. Allow the tube to stand in bright sunlight.

white precipitate which turns [1]

[1]

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(c) Suggest the names of two salts that may be contained in solid X.

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2 [2]

(d) Write a balanced symbol equation for the chemical reaction seen in test (a)(ii).

[1]

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3 When a light ray passes through a rectangular glass block, the ray is displaced from its original path onto a new path. This is shown in Fig. 3.1.

normal

normal

incident ray

angle ofincidence

i

rectangularglass block

original path ofincident ray

d displacementnew path oflight ray

Fig. 3.1 A student is doing an experiment to find out how the value of the displacement distance, d,

varies with i, the angle of incidence.

• He places a glass block on a sheet of paper and draws the outline of the block on it.

• He shines a narrow beam of light through the glass block.

• He marks the path of the incident ray on the paper.

• He measures i, the angle of incidence, and records the value in Table 3.1.

• He marks the new path of the light ray on the opposite side of the block.

• He removes the glass block from the paper and extends the line showing the original path of the light ray.

• He measures the displacement distance, d, shown in Fig. 3.1, to the nearest millimetre and records it in Table 3.1.

• He repeats the experiment, each time using a different angle of incidence, and records the results in Table 3.1.

Table 3.1

experiment number 1 2 3 4 5

angle of incidence, i / ° 15 28 46 77

displacement, d / mm 5 11 20 47

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(a) Fig. 3.2 shows his diagram for experiment 4.

angle i

angle i

width w

glass block

d displacement

length l

incident ray

Fig. 3.2 (i) On Fig. 3.2, measure i, the angle of incidence, to the nearest degree. Record it in

Table 3.1. [1] (ii) On Fig. 3.2, measure the displacement distance, d, in millimetres to the nearest

millimetre, and record it in Table 3.1. [1] (iii) On Fig. 3.2, measure the length, l, and the width, w, of the glass block in millimetres

to the nearest millimetre.

l = mm

w = mm [2]

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(b) (i) On the graph grid provided, plot a graph of the displacement distance, d, (vertical axis) in millimetres against the angle of incidence, i. Use values of i from 0 to 90°, and values of d from 0 to 80 mm.

Draw a smooth curve through the points and extend the line to the point i = 90°.

[3] (ii) Use your graph to find the value of the displacement distance, d90, when the angle

of incidence is 90°. Show how you do this on the graph.

d90 = mm [2]

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(c) Compare your answers to parts (a)(iii) and (b)(ii). Complete this sentence.

“In theory, if the angle of incidence of a light ray passing through a rectangular

glass block is equal to 90 degrees, the displacement distance is equal to the

of the block.” [1]

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4 (a) A student was studying cells under a microscope. She prepared cells from onion epidermis, placed them onto a slide and stained them using iodine solution.

The student wanted to measure the average length of epidermis cells. She placed a

ruler with a millimetre scale on the stage of the microscope to find the diameter of the field of view. She looked down the microscope and saw the field of view in Fig. 4.1.

mm

field of view

ruler

Fig. 4.1

(i) How wide is the field of view of the microscope? mm [1]

(ii) The student removed the ruler and placed her slide under the microscope. She

counted 15 cells end to end across the field of view. Use your answer to (a)(i) to calculate the average length of an onion cell. Show your working.

length of cell mm [2]

(b) A group of cells is shown in Fig. 4.2.

cell A Fig. 4.2

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(i) Make a large drawing of cell A in the space provided. Label the nucleus and cell wall.

[1] (ii) Measure the length of cell A on your diagram at the longest part. See Fig. 4.3.

length of cell

cell A

Fig. 4.3

length of cell A on my diagram mm

Using the value for the average cell length from (a)(ii) and the length of cell A on

your diagram, calculate the magnification of your drawing.

magnification = [3]

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(c) The student looked at a diagram of a plant cell in a text book. This cell came from a leaf. It is shown in Fig. 4.4.

Fig. 4.4 (i) Label one structure on Fig. 4.4 that is not present in onion epidermis cells. [1] (ii) Suggest a reason why this structure is missing from onion epidermis cells.

[1]

(iii) Label one structure on Fig. 4.4 that is present in onion epidermis cells but not

visible in Fig. 4.2 or Fig. 4.3. [1]

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5 The science teacher has asked the class to plan an experiment to compare the amount of acid in an orange, a lemon and a grapefruit. The acid in these fruits is citric acid.

The students have made a list of the steps in the experiment.

• Cut the orange with a knife and squeeze out the juice.

• Filter the juice and place it in a conical flask.

• Add a few drops of indicator.

• Add sodium hydroxide solution from a burette until the indicator changes colour.

• Note the volume of sodium hydroxide solution used.

• Repeat the steps above using a lemon and a grapefruit.

(a) (i) Name an indicator suitable to use in this experiment and give its colours in acid

and in alkali.

name of indicator [1]

colour in acid

colour in alkali [1]

(ii) Suggest the name of the salt formed when citric acid reacts with sodium hydroxide.

[1]

(b) The students carry out the experiment. Table 5.1 shows the results. Table 5.1

juice orange lemon grapefruit

first burette reading / cm3 0 0.8 4.7

second reading / cm3

volume added / cm3

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(i) Fig. 5.1 shows the burette scales for the second readings. Read the burette scales and record the results in Table 5.1. [3]

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9

10

11

12

13

orange

21

22

23

24

25

26

lemon

second readings of burette

15

16

17

18

19

20

grapefruit

Fig. 5.1 (ii) Complete Table 5.1 to show the volumes of sodium hydroxide added. [1] (iii) List the three fruits in order of the amount of acid they contain, with the fruit

containing the most acid first.

1 (most acid)

2

3 (least acid) [1]

(c) Suggest two ways in which this experiment must be modified so that the concentration

of acid in the fruit juices may be measured, assuming that the same kind of acid is contained in each fruit.

1

2

[2]

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6 The teacher is showing the class an apparatus for investigating the expansion of metals. A metal bar is heated to a known temperature to find the increase in its length. Fig. 6.1

shows the apparatus.

0

thermal sensor

digitalreadout

heater support

zero adjusterpointer

scale

zinc bar

Fig. 6.1 Fig. 6.2 shows how the pointer measures the increase in length of the bar.

0

1

2cm

scale20 cm

2 cm

pointer

zero adjuster

pivot

balancingweight

end of zinc bar

Fig. 6.2

• The teacher places a zinc bar of length 20 centimetres on the supports.

• He adjusts the pointer until the scale reads 0 cm.

• He slowly heats the bar until the thermal sensor reads 300 °C.

• He reads the position of the pointer on the scale and records it in Table 6.1.

• He repeats the experiment with bars of three other metals.

Table 6.1

metal zinc iron aluminium copper

pointer reading / cm 1.8

expansion / mm

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(a) The pointer and scale for the metals iron, aluminium and copper are shown in Fig. 6.3. Read the scales. In Table 6.1, record the readings in centimetres to the nearest

millimetre. [3]

0

1

2cm

pointer readingfor iron bar

0

1

2cm

pointer readingfor aluminium bar

0

1

2cm

pointer readingfor copper bar

Fig. 6.3 (b) (i) Explain why the expansion of the bar is found by dividing the pointer reading

by 10. Use Fig. 6.2 to help you.

[2]

(ii) Calculate the expansion of the bars in millimetres and complete Table 6.1. [1] (c) Use the data in Table 6.1 and place the metals in order of the amount that they

expanded.

1 (most expansion)

2

3

4 (least expansion) [1]

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(d) Fig.6.4 shows atoms in a solid metal.

Fig. 6.4 (i) Describe the motion of the atoms in a solid metal. You may draw on Fig. 6.4 to

help your description.

[1]

(ii) Explain why heating the metal causes it to expand.

[2]